There are good things about complete rebuilds and then there are bad things about them.
Obviously, rebuilding teams, whether they are bottomed out or just really bad, brings quite a sense of accomplishment when you finally make them playoff contenders. No one can dispute the accomplishment of taking a bottom feeder and making them nationally relevant.
However, coaches that do rebuilds often rely on the "it was a rebuild" excuse for why they don't win in-game accolades or measure up to others' accomplishments. Plus, its an easy cop-out that usually doesn't gain a lot of respect. Add to that the fact that most rebuilds are done at the D3 level where its really not that hard to do rebuilds in the first place, especially now that many of the veteran campers are gone. Listen, it does take some skill to rebuild a crap team (maybe not more than taking a good team and making them great, however) but If you want to really impress people with your rebuild skills, try getting Purdue to a level 5 bowl game. Then you will earn mad respect!